The invention relates to marine propulsion systems having an exhaust elbow extending from the engine and discharging engine coolant water into the engine combustion product exhaust.
Various exhaust elbows for marine propulsion systems are known, for example as shown in Sarra U.S. Pat. No. 3,541,786. The elbow extends from the engine manifold and has separate intake passages for exhaust and for water. The elbow discharges mixed exhaust and water.
Water ingestion is a significant problem in exhaust elbows for marine propulsion systems. Engine pulsations due to reciprocating piston movement tends to suck any water within or at the outer tip of the elbow back into the engine, which is undesireable. Water can tend to collect at the discharge end tip of the elbow where coolant water is discharged into the exhaust to mix therewith. Water or moisture deposited or formed at this outer tip end actually travels backwards into the interior of the exhaust passage within the elbow in a pulsating manner and eventually back into the engine. This pulsating ingestion becomes more pronounced with increasing engine size.
Besides the water formation at the outer end discharge tip, water ingestion can also be caused by condensation within the exhaust passage of the elbow. This condensation is due to the temperature differential between the hot exhaust passage within the elbow and the cooler water jacket therearound.
The present invention addresses and solves the above noted problems. The invention minimizes water deposits at the outer discharge tip end of the elbow. The invention also minimizes condensation within the elbow.